In ultrasound imaging devices, images of a subject are created by transmitting one or more acoustic pulses into the body from a transducer. Reflected echo signals that are created in response to the pulses are detected by the same or a different transducer. The echo signals cause the transducer elements to produce electronic signals that are analyzed by the ultrasound system in order to create a map of some characteristic of the echo signals such as their amplitude, power, phase or frequency shift etc. The map therefore can be displayed to a user as images.
One class of transducer is a Micromachined Ultrasound Transducer (MUT), which can be fabricated from, for example, silicon and configured to transmit and receive ultrasound energy. MUTs may include Capacitive Micromachined Ultrasound Transducer (CMUTs) and Piezoelectric Micromachined Ultrasound Transducer (PMUTs). MUTs can offer many advantages over other conventional transducers such as, for example, lower cost of production, decreased fabrication time, and/or wider frequency bandwidth. MUTs, however, can be fragile and are typically utilized in single-use internal ultrasound imaging applications.
The use of a transducer in an external probe generally involves bonding or otherwise attaching an acoustic lens to the transducer. The acoustic lens can protect the transducer from damage and/or may also provide acoustic focusing into a subject. In some low frequency applications, MUTs may be utilized in external probes having acoustic lenses made from, for example, an elastomer material. However, these elastomer lenses may not be suitable for high frequency ultrasound applications (e.g., greater than about 15 MHz) due to, among other reasons, increased acoustic attenuation of the materials at the higher frequencies. Accordingly, a need for a low-loss and durable acoustic lens exists for an external MUT probe suitable for use at higher frequencies.